I do have SpeedTuning chip on my C43 and there is a huge difference in how fast the RPM gets to the top end and it is definitely faster compared to stock. I also have the drive pulleys from * and RamAir filter, but I don't know how much more horsepower it increased. SpeedTuning told me that the HP should increase to 332 (306 Euro version). So maybe with the drive pulleys and air filter, another 5-8%. It's not bad for the money.
I'm planning to try * SC on my other C43, which is currently stock.
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